In the field of organic synthetic chemistry, an approach of protecting functional groups with protecting groups is often adopted in order to prevent unintended chemical reactions. Various groups are known as such protecting groups. For example, a benzyl group is generally used for the protection of —OH or >NH in a carboxy group, a hydroxyl group, an amino group, an amide group, a sulfonamide group, and the like. In most cases, protecting groups are to be removed at any stage and thus have the property of being easily cleavable according to need. The benzyl group usually has the property of being easily cleaved by hydrogenolysis reaction, oxidation reaction, or treatment with a Lewis acid or the like, and is frequently used. Also, a methoxy-substituted benzyl group in which 1 to 3 methoxy groups are introduced in the phenyl group of the benzyl group particularly has the property of being also eliminable by acid treatment and is advantageous in that this group can be removed without adopting reductive conditions (Non-Patent Literature 1).
A compound having a benzenesulfonamide structure is known as an analgesically active compound. In the production of this compound, an intermediate containing a 2,4-dimethoxybenzyl group bonded to the nitrogen atom of a sulfonamide group is adopted and converted to the objective compound through cleavage of this 2,4-dimethoxybenzyl group by acid treatment (Patent Literatures 1 to 4).